add prep code for proper text-validator for text-input gui-widget
add spawner block to handled blocks for template system  
restructure exception handling in template parsing to more clearly state
what went wrong and where.  
also fixed template parsing to parse old templates, moved exception
handling for rules out to templateParser class.  
clean up an error in nbt-tools where it would not parse an empty
string-nbt tag properly
add lookup table for unlocalized block names, as fail-through handling
for block lookup.  
add default return for not-found block to be blocks.air  
update structure-preview image size to 512*288  
add check to disable builders building below y=1  
update layout on structure-selection GUI to enable structure-preview
images